The present invention relates to a gauge for measuring parts, and particularly, though not exclusively, for determining the contour of a sheet.
The present invention is particularly, though not exclusively, suitable for measuring automotive glass, to which application reference is made herein purely by way of example.
Gauges for measuring automotive glass are known, which substantially comprise a rigid structure with a peripheral supporting band corresponding to the theoretical contour of the glass; and the band, on which the glass is placed, is equipped with a number of appropriately spaced position transducers connected to a data processing system and for detecting any departure of the corresponding edge points of the glass from the supporting band.
Though fast, easy to use, and therefore suitable for on-line measuring all production parts, gauges of the type briefly described above present several drawbacks.
In particular, being special-purpose fixtures of a shape strictly related to the part being measured, a special gauge is required for each part, thus resulting in considerable cost in terms of fabrication and storage of the gauges.
Moreover, the actual fabrication of each gauge is a fairly painstaking job, normally involving computer-aided machining of an aluminium alloy model or master on the basis of a computer-aided-designed mathematical model of the supporting band. A first plastic resin cast or "negative" is made from the master and, from the "negative", a second plastic resin cast or "positive" is made to reproduce the master and which forms the rigid structure of the gauge to which the transducers are fitted.
Finally, the accuracy obtainable using the above method is fairly poor.